docs: def convert(self):
          """Convert spectral response functions from wavelength to wavenumber"""
  
          from pyspectral.utils import (convert2wavenumber, get_central_wave)
          if self._wavespace == WAVE_LENGTH:
              rsr, info = convert2wavenumber(self.rsr)
              for band in rsr.keys():
                  for det in rsr[band].keys():
                      self.rsr[band][det][WAVE_NUMBER] = rsr[
                          band][det][WAVE_NUMBER]
                      self.rsr[band][det]['response'] = rsr[
                          band][det]['response']
                      self.unit = info['unit']
                      self.si_scale = info['si_scale']
              self._wavespace = WAVE_NUMBER
              for band in rsr.keys():
                  for det in rsr[band].keys():
                      self.rsr[band][det]['central_wavenumber'] = \
                          get_central_wave(self.rsr[band][det][WAVE_NUMBER], self.rsr[band][det]['response'])
                      del self.rsr[band][det][WAVE_LENGTH]
          else:
              errmsg = "Conversion from {wn} to {wl} not supported yet".format(wn=WAVE_NUMBER, wl=WAVE_LENGTH)
              raise NotImplementedError(errmsg)